Method for monitoring energy supply in a vehicle

Abstract

Determine ways to make energy supplies more reliable. [Solution] A method for monitoring the energy supply of a motor vehicle, characterized in that at least one supply path (59) is provided for supplying electrical energy, in particular to a safety-relevant load (16, 25), the supply path (59) including at least two current-carrying components (60, 62) connected in parallel and protecting the load (16, 25), in particular switching means (60) and / or fuses (62), the value of at least one electrical characteristic quantity (R), in particular an electrical resistance (R), representative of the function of the supply path (59), is determined, at least one electrical measured quantity (U, I) applied to at least one of the components (60, 62) is detected, the electrical characteristic quantity (R) is determined as a function of the measured quantities (U, I), an inspection of at least the electrical characteristic quantity (R) is performed, and the current-carrying components (60, 62) and the supply path (59) are at least partially arranged in a control device (78).

Description

[Technical Field]

[0001] The present invention relates to a method for monitoring the energy supply of a motor vehicle according to the preamble of the independent claim. [Background technology]

[0002] German Patent Application No. DE 10 2018 212 369 A1 discloses a method for monitoring the energy supply of a motor vehicle, in which at least one energy accumulator supplies energy to preferably a plurality of safety-relevant loads in a partial on-board electrical grid, at least one measured quantity of the energy accumulator and / or of the at least one load is detected, at least one wiring harness model representing the partial on-board electrical grid is provided, and a parameter estimator is provided for estimating at least one characteristic quantity of the wiring harness model using the measured quantity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] German Patent Application Publication No. 102018212369 Summary of the Invention [Problem to be solved by the invention]

[0004] The invention is based on the problem of defining a method for further increasing the reliability of the energy supply. This problem is solved by the features of the independent claims. [Means for solving the problem]

[0005] The reliability of the energy supply can be further increased by monitoring the power supply paths in the control device, in particular for safety-relevant loads. In particular, by monitoring the electrical resistance of the current-carrying paths and components, and preferably their terminals, the diagnostic scope can be expanded to the entire energy supply path, in particular for safety-relevant loads. By means of suitable measurement methods, such as differential voltage measuring amplifiers, and corresponding calculation methods using characteristic quantity estimation methods, it is possible to continuously and accurately determine characteristic quantities inside the control device, such as resistance, over time.

[0006] By using a parameter estimator to determine the electrical characteristic or electrical resistance value, it is possible to eliminate a large portion of the measurement errors that may appear as both random and systematic error quantities during the measurement.

[0007] It is particularly preferred to use static thresholds for identifying the error information, for example, nominal values ​​(e.g., resistance values) specified by the manufacturer of the current-carrying component. If the estimated characteristic value of the component significantly deviates from its nominal value, this can be used as error information, for example, by entering it in an error memory or by forwarding the error information to a higher-level energy management system for further processing, for example, as a warning to the driver or a decrease in driving operability. This further increases the safety of the vehicle.

[0008] It is particularly advantageous that the above-described monitoring principle can be extended to various circuit configurations, in particular parallel circuits of various current-carrying components, by selecting suitable current and voltage measuring points before the branch and / or at the beginning or end of the current path, e.g., at the contacts, so that in addition to the resistances of the current-carrying components, the resistances of the supply lines and / or contacts can also be taken into account and used for fault location.

[0009] In an advantageous improvement, the threshold value is flexibly selected depending on the resistance model, so that a shift in the operating point due to, for example, changing temperature conditions cannot lead to an error trigger, which further increases the safety of the device.

[0010] In an advantageous refinement, the current state of the measured values ​​is checked and, if necessary, a new determination is made, thereby providing reliable and up-to-date information on functionality. Further advantageous refinements are set forth in the further dependent claims and the description. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of a power divider that connects two partial on-board power supply networks. [Figure 2] FIG. 10 is a diagram showing values ​​to be detected in a parallel circuit of two energization switching means. [Figure 3] FIG. 10 is a diagram showing values ​​to be detected in a parallel circuit of two energization fuses. [Figure 4] FIG. 10 is a diagram showing values ​​to be detected in a parallel circuit of two energization switching means and two energization fuses. [Figure 5] FIG. 5 shows a measurement device for determining the total characteristic quantity of the device shown in FIG. 4. [Figure 6] FIG. 1 illustrates the structure of a Kalman filter type estimation method. [Figure 7] FIG. 1 illustrates an apparatus for identifying a soft threshold. [Figure 8] FIG. 6 shows an extension of the measuring device shown in FIG. 5. [Figure 9] 1 is a perspective view showing the current-carrying parts of the device inside the control device and the associated structures of the further device that determine the overall characteristic quantities of the device. [Figure 10] 10A-10C illustrate further device structures identifying further extended current paths. DETAILED DESCRIPTION OF THE INVENTION

[0012] The invention is illustrated schematically by way of an embodiment and will be explained in more detail below with reference to the drawings. FIG. 1 shows a possible topology of an energy supply system. It consists of an on-board power supply network 13, which includes an energy storage device 12, in particular a battery 12 with associated sensors 14, preferably battery sensors, and particularly safety-relevant loads that are protected or controlled by a power distributor 18. The loads 16 are special loads with high demands or need for protection, commonly referred to as safety-relevant loads 16. These are, for example, electric steering and / or braking systems, components that must be powered to ensure the vehicle can steer and / or brake in the event of an error. The characteristic values ​​of each load 16 are detected individually, and a respective switch 15 is opened in the event of a deviation from a tolerance. The on-board power supply network 13 consists of a safety-relevant on-board power supply network 11 and a non-safety-relevant on-board power supply network 10. The safety-relevant on-board power supply network 11 can be disconnected from the non-safety-relevant on-board power supply network 10 by the power distributor 18, in particular in the event of an error or critical state in the non-safety-relevant on-board power supply network 10. The safety-related partial onboard power supply network 11 is, for example, an ASIL-compliant (for example according to DIN ISO 26262) partial onboard power supply network 11 and comprises at least one safety-related load 16 and may possibly be equipped with its own energy accumulator 12 for voltage support. The non-safety-related partial onboard power supply network 10 comprises at least one non-safety-related load 17, which may, for example, be a so-called QM load. However, it cannot be excluded that at least one further safety-related load is also arranged in the non-safety-related partial onboard power supply network 10, for example if the safety-related loads are configured redundantly. The non-safety-related partial onboard power supply network 10 is a non-ASIL-compliant onboard power supply network.

[0013] An energy accumulator 12 is also connected to a terminal (connection terminal KL30_1) of the power distributor 18. The sensor 14 can detect electrical characteristic quantities such as the voltage Ub at the energy accumulator 12, the current Ib flowing through the energy accumulator 12, and / or the temperature Tb of the energy accumulator 12. The sensor 14 can use the determined electrical characteristic quantities Ub, Ib, Tb to determine, for example, the state of charge SOC of the energy accumulator 12 or other characteristic quantities of the energy accumulator 12. At a further terminal (KL30_1) of the power distributor 18, to which the energy accumulator 12 is also connected, an optional further supply branch for at least one further load 25 is also provided. By way of example, the load 25 is protected by a safety fuse 23. Further loads 25 may also be provided, which can also be protected by the safety fuse 23. These loads 25 are loads which must be supplied with power from the energy accumulator 12 even when the switching means 19 of the power distributor 18 are disconnected or opened, and are preferably safety-critical loads 25 with regard to supply guarantee failures. In this way, (optional) safety-related or safety-critical on-board power supply network paths or partial on-board power supply networks 11 are connected to terminal KL30_1.

[0014] The power distributor 18 can determine corresponding characteristic quantities, such as the voltage Uv and current Iv of the load 16. Furthermore, the power distributor 18 can determine corresponding characteristic quantities, such as the voltage Ub and / or the current Ib and / or the temperature Tb, of the energy storage device 12. For this purpose, the power distributor 18 includes a corresponding sensor system or receives data from the sensors 14. The power distributor 18 also has corresponding evaluation means 21, such as a microcontroller, for storing or evaluating detected values. The evaluation means 21 is used, in particular, to identify critical states of the safety-relevant partial onboard power supply network 11, such as detecting overcurrents and / or undervoltages or overvoltages for the safety-relevant loads 16, 25 on the partial onboard power supply network 11. For this purpose, the corresponding characteristic quantities are detected and compared with appropriate threshold values. For example, a microcontroller is used as the evaluation means 21. Furthermore, the microcontroller or evaluation means 21 can also control the corresponding switch 15, the switching means 34 of the high-current-capable circuit breaker 34 of the main path 30, or the switching means 54 of the additional path 50. The additional path 50 is connected in parallel to the main path 30. The additional path 50 comprises a switching means 54 and a resistor 58, in particular a current-limiting resistor 58, arranged in series with the switching means 54. In normal operation, the two paths 30, 50 are active in parallel, i.e. their switching means 34, 54 are closed. Furthermore, the additional path 50 is used to pre-charge the non-safety-related partial onboard power supply network 10, for example when an energy accumulator is connected to the safety-related partial onboard power supply network 11 for the first time. Due to the capacitive components of the non-safety-related partial onboard power supply network 10, high charging currents are ensured via the additional path 50, which also needs to be protected from overload in this situation.

[0015] The switching means 34 can in particular realize a corresponding disconnection or connection function of the two on-board power supply network branches (the partial on-board power supply network 10 for the non-safety-relevant loads 17 at terminal KL30_0 and the further partial on-board power supply network 11 for the safety-relevant loads 16, 25). This serves in particular as a safety function to prevent the effects of critical conditions such as overvoltage or undervoltage, and / or overcurrent, and / or thermal overload. In the event of a fault, the two partial on-board power supply networks 10, 11 can be disconnected from each other by the power distributor 18 by opening the switching means 34, 54.

[0016] The onboard power supply network 13 has a lower voltage level U1 than the optional high-voltage onboard power supply network 20, and may be, for example, a 14-volt onboard power supply network. A DC voltage converter 22 is arranged between the onboard power supply network 13 and the high-voltage onboard power supply network 20. The high-voltage onboard power supply network 20 includes, by way of example, an energy storage device 24, e.g., a high-voltage battery, possibly with an integrated battery management system, as well as loads 26, e.g., comfort loads such as an air conditioning system, which are supplied at a higher voltage level, and electrical equipment 28. In this context, high voltage is understood to mean a voltage level U2 that is higher than the voltage level U1 of the basic onboard power supply network 13. This may be, for example, a 48-volt onboard power supply network. Alternatively, an even higher voltage level may be used, particularly in vehicles with electric drives. Alternatively, the high-voltage onboard power supply network 20 may be omitted entirely.

[0017] By way of example, the embodiments describe batteries or accumulators as possible energy stores 12, 24. However, alternatively, other energy stores suitable for the task may be used, such as inductive or capacitive based, fuel cells, capacitors, etc.

[0018] Particularly preferably, the switching means 34, 54 are each formed by at least two switching elements connected in anti-series (series opposite to each other, e.g. "back to back" or with a common source terminal), preferably using power semiconductors, particularly preferably FETs (field-effect transistors) or MOSFETs (metal-oxide-semiconductor field-effect transistors). Instead of MOSFETs, for example, relays, bipolar transistors or IGBTs (insulated gate bipolar transistors) with parallel diodes etc. may also be used.

[0019] 2 to 10, the diagnostic scope of the complete energy supply path 59 can be expanded by monitoring, in particular, the internal connections and energy supply paths 59 within the control device 78. The basic idea of ​​the internal monitoring of the supply paths 59 and terminals within the control device is based on monitoring electrical characteristic quantities, in particular the electrical resistance R of the current-carrying paths and components 60, 62, connections or contacts 74 within the control device. By using suitable measurement methods, such as a differential voltage amplifier or measurement amplifier 66, and corresponding calculation methods, such as the parameter estimation method implemented in the parameter estimator 68, it is possible to continuously and accurately determine the resistance R within the control device as an electrical characteristic quantity over time.

[0020] In the example shown below, the diagnosis is carried out in two steps: First, the electrical characteristic quantities, such as the electrical resistance R of a component or current path, are determined using parameter estimation methods based on the measured quantities U, I (as the value of the current I flowing through the component or the value of the voltage U dropped across the component). The results are then analyzed and, if necessary, subsequent system reactions are initiated.

[0021] 2 and 3, the first application example is the diagnosis of the electrical characteristics of an energization element, such as a switching means 60 (FIG. 2), e.g., a transistor, particularly preferably a MOSFET, or a fuse 62 (FIG. 3). A current I flows through the energization elements 60, 62, and a voltage U drops across them. Determining the resistance R of the energization elements or components 60, 62 requires measuring the differential voltage U present between the two component terminals or between the components. The supply path 59 consists of two parallel-connected partial paths, each of which includes a corresponding energization component 60, 62, such as a switching means 60 or a fuse 62, that protects the safety-relevant loads 16, 25, at least partially located within the control device 78. In high-safety applications, partially redundant hardware is used so that the redundant design can continue to maintain overall operation even if a part of the system fails. This is exemplified in FIGS. 2 and 3 by the corresponding parallel-connected switching means 60 (FIG. 2) or fuse 62 (FIG. 3). In principle, this method can also be applied to the structures shown in Figures 2 or 3. In practice, further combinations of two or more parallel-connected switching means 60 and / or two or more parallel-connected fuses 62 occur, resulting in the exemplary structure shown in Figure 4. Here, at least two switching means 60 and at least two fuses 62 are exemplarily connected in parallel with one another. The supply path 59, which is at least partially arranged in the control device 78, has four parallel, and thus redundant, sub-branches in this example. These are supplied with the current I flowing upstream of the parallel branch. A voltage U drops across current-carrying components and components protecting the safety-relevant loads 16, 25, such as the switching means 60 and the fuses 62.

[0022] 5, the structure shown in FIG. 4 is exemplarily shown, where the differential voltage U is measured using a suitable voltmeter, such as a differential amplifier 66. The current I is measured by a corresponding measuring device, such as a measuring resistor 64 or a measuring shunt. The output values ​​of the measuring resistor 64, as the value of the flowing current I, and the output values ​​of the differential amplifier 66, as the value of the voltage U, are fed to a parameter estimator 68. The parameter estimator 68 is used, in particular, to determine electrical characteristic quantities, such as the resistance R, of the current-carrying components 60, 62, while eliminating most of the measurement errors that may appear during the measurement as both random and systematic errors.

[0023] When all MOSFETs 60 and fuses 62 in a paralleled component are operating intact, a total current I flows through all four components 60, 62. The total conductance G of the component can be calculated as the sum of the electrical conductances of the four components 60, 62. If the conductance of at least one of the components 60, 62 deteriorates, or in the worst case scenario, a connection to the circuit board (such as a solder joint) becomes loose, this is reflected either directly in the conductance G or in the resistance R of the entire component or the entire supply path 59. The total conductance G decreases, and the total resistance R increases. As a simple example, assuming all components 60, 62 have the same resistance at rated operation, removing one of the four parallel-connected components 60, 62 increases the total resistance R by approximately 33%.

[0024] If the total resistance R is constantly monitored during operation using the measurands U and I and a resistance monitoring device or parameter estimator 68, the removal of one of the four components 60, 62 can be immediately recognized based on the change in the total resistance R. Potential errors can therefore be detected. In principle, with sufficient current excitation, a deterioration in the resistance R can also be detected. Figure 5 shows the configuration of such a device for determining the resistance R.

[0025] If the change in the estimated resistance value R of the structure described in FIG. 4 exceeds a certain limit value Rg, this can be registered as an error and a corresponding reaction can be triggered (e.g., entry into an error memory or forwarding of the error information to a higher-level energy management system for further processing, e.g., warning the driver or reducing driving operability).

[0026] If no components have been removed but the electrical conductivity G of the individual components (switching means 60 and / or fuses 62) has decreased, this decrease will also be reflected in the total resistance R and can therefore also be considered a potential error.

[0027] Here, the equivalent resistance of the parallel structure is

[0028]

number

[0029] The resistance R is the corresponding characteristic of this network model, which is very simple for most applications and is expressed as the parameter vector

[0030]

number

[0031] will be integrated as The existing voltage and current measurements are entered as U and I in the above equivalent circuit diagram, and in the following equation, U FET+FUSE (or as differential voltage U D ) or I FET+FUSE It is described as:

[0032] According to Ohm's law, the following equations are obtained that represent the network model:

[0033]

number

[0034] This equation is expressed in terms of the characteristic quantities of the object, i.e., the parameter vector

[0035]

number

[0036] The resistance R can be written in the form of a parameter vector

[0037]

number

[0038] is calculated using the parameter estimator 68 as the measurement vector z k can be updated at each new time step with reference to the corresponding measurements, which are integrated into In the following, the corresponding values ​​are combined into corresponding vectors or matrices as already explained.

[0039]

number

[0040] To recursively solve the system of equations, in an embodiment a so-called Extended Kalman Filter (EKF) is used as parameter estimator 68. Alternatively, other parameter estimators 68 such as (recursive) least squares methods or other state estimators such as standard / nonlinear Kalman filters, particle filters or similar estimation / optimization methods may be used.

[0041] On-line estimation and correction of systematic measurement errors Basically, measurement errors, i.e. errors in real measurement processes, consist of systematic (cognitive) errors and random (accidental) errors. The latter arise from random physical processes and cannot be influenced without changing the physical measurement principle. Systematic errors, however, are based on deterministic correlations. If it were possible to estimate these correlations online, i.e. during operation, this source of error could be eliminated.

[0042] To do this, traditional estimation models can be extended to include so-called disturbance models. Disturbance models represent the influence of unknown states on the measurement result, in this case systematic measurement errors. To correct for systematic measurement errors, these unknown parameters must be estimated in addition to the resistance. This is possible if there are enough measurement points (observability).

[0043] A common model for real-world systematic measurement errors is a linear relationship.

[0044]

number

[0045] Here, m represents the physical quantity to be measured, such as the current I or the voltage U.

[0046]

number

[0047] is a measurement that generally has deviation.

[0048]

number

[0049] corresponds to the gain and bias (a constant amount of overlap). For a perfect sensor, a = 1 and b = 0. If a and b can be estimated (also called calibration), systematic measurement errors can be corrected.

[0050] Generally, there are multiple sensors and corresponding systematic measurement errors. However, only the cumulative effect of these errors is relevant to the resistance estimation. Therefore, the number of additional parameters to be estimated can be significantly reduced, which usually makes calibration possible. When estimating the equivalent resistance of the parallel structure and the corresponding measurement points, the voltage U D becomes:

[0051]

number

[0052] Now, assuming the above model for systematic measurement error, we have:

[0053]

number

[0054] Therefore, to correct the bias error, the bias

[0055]

number

[0056] Instead of bias

[0057]

number

[0058] The same can be done for the gain error, depending on whether or not a measurement point is available. The same procedure applies here. If a suitable excitation is present, it is also possible to combine the two calibration methods.

[0059] Furthermore, an estimate of the systematic measurement error may be used to diagnose the measurement point and to detect the presence of an error if the error is large. This additional information is fundamental for a sufficient ASIL qualification, taking into account the diagnosability of the measurement point.

[0060] If an estimation method is used that also takes into account random measurement error, the measurement formula can be extended to include the random quantity

[0061]

number

[0062] is required.

[0063]

number

[0064] Parameter estimates are calculated by dividing other parameters by

[0065]

number

[0066] and

[0067]

number

[0068] is adjusted by including An estimation method, such as a Kalman filter, provides estimates of the resistance R and the cumulative parameters of the measurement equation with minimal variance, i.e., the highest possible estimation quality.

[0069] The structure of the Kalman filter as an essential component of the parameter estimator 68 is shown in Figure 6. The parameter estimator 68 includes at least one predictor 67 or time updater. An initial estimate of the state value xk

[0070]

number

[0071] and the initial estimate Pk-1 of the error covariance Pk are sent as inputs to the prediction unit 67. In the steady state, the currently specified output values ​​from the correction unit 69 (or the measurement update unit), i.e., the latest parameter vector xk and the latest error covariance Pk, are sent as inputs to the prediction unit 67.

[0072] The update or time update is performed in the predictor 67. This includes a state prediction of the state variables xk in the form:

[0073]

number

[0074] Furthermore, the prediction unit 67 predicts the error covariance matrix Pk in the form of the following equation.

[0075]

number

[0076] where:

[0077]

number

[0078] Output Value

[0079]

number

[0080] and

[0081]

number

[0082] is sent as an input to the correction block 69, where the estimates are updated based on the measurements. First, the so-called Kalman gain

[0083]

number

[0084] is calculated by the following formula:

[0085]

number

[0086] where:

[0087]

number

[0088] Subsequently, the correction unit 69 updates the estimate based on the measurement according to the following equation:

[0089]

number

[0090] Finally, the correction unit updates the error covariance Pk according to the following equation:

[0091]

number

[0092] Here, I corresponds to the identity matrix. Thus, the characteristic quantity

[0093]

number

[0094] The expectation and covariance of are estimated. In the first step of the filtering process, the previous estimates are applied to the state dynamics to obtain a prediction for the latest time point. The predictions are corrected in the correction block 69 using the new information from the latest measurements to obtain the required updated estimates.

[0095] FIG. 7 describes how to determine the threshold value Rn. In the previous examples, the results were evaluated using a threshold value of the maximum resistance value Rn. This nominal value can be derived, for example, from the specifications of the components 60 and 62 or from existing knowledge or experience in function development. The threshold value Rn can be a fixed value, but it can also be designed as a calculation model. The calculation model can adjust the threshold value Rn accordingly depending on the latest operating point. Other external influences, such as temperature T, can be taken into account to determine the latest operating point.

[0096] This is shown in FIG. 7 as an example. A resistance monitoring device 86 determines the current resistance Rm of the parallel-connected switching means 60 and / or fuse 62 based on the measured values ​​of voltage U and current I. As an example, two parallel circuits of switching means 60 and fuses 62 are provided as components for protecting current-carrying components and safety-relevant loads 16, 25 in a load distributor 18 with an associated supply path 59 in a control device 78. In parallel, a nominal resistance Rn or a threshold Rn is calculated online using a resistance model 88. The resistance model 88 is illustratively implemented as a thermal model. The resistance model 88 determines the nominal resistance Rn based on the measured component temperature T. The results are analyzed in a downstream evaluation unit 90 (hardware error monitor). Error information 92 is generated based on a comparison of the output value Rm (estimated resistance Rm) of the resistance monitoring device 86 with the output value Rn and threshold Rn of the resistance model 88. An error reaction corresponding to this error information 92 may be made, for example, by inputting it into an error memory, or the error information 92 may be forwarded to a higher-level system, such as an energy management system, for further processing, for example in the form of a warning to the driver or a reduction in driving performance. Furthermore, a debounce function is provided to debounce or avoid falsely detected errors, which, for example, reports an error 92 only if the estimated resistance value Rm exceeds an acceptable threshold a number n of times in a row.

[0097] As a simple example, assuming that all components 60, 62 have the same resistance value at rated operation, if one of four components 60, 62 connected in parallel is omitted, the total resistance value will increase by approximately 33% relative to the original total resistance value.

[0098] A further part of the system monitors the current status of the determined resistance value Rm. The vehicle's usability depends on whether the required test intervals of the control unit 78 are observed. If reliable values ​​are not available for a long period of time, no reliable statement can be made about functionality. This is done by storing the readings of a counter in the non-volatile memory of the computer unit. The counter counts defined test cycles (e.g., driving cycles or on / off cycles of terminal 15) and takes defined measures if a limit value is exceeded.

[0099] If the latest resistance value Rm is not available, the following method is used. Step 1: Request the vehicle to generate a load pulse. Step 2: If the request fails, generate a driver message.

[0100] The embodiment according to FIG. 8 is an extension of the previous application examples. The control device 78 contains a great many electrical networks which in principle can be considered as a combination of the previous arrangements. Parts of the circuit boards used in the control device 78 can also be considered as part of the current-carrying paths. If in each current path it is possible to measure the current, for example by means of a measuring resistor 64, then the components (switching means 60 and / or fuses 62, possibly connected in parallel with the switching means 60 and / or fuses 62) and the copper rail (line resistance R Cu ) can be used to determine the resistance of the individual current paths.

[0101] Figure 8 shows an example of a simple network consisting of two intersecting current paths. Each branch contains components such as switching means 60 and / or fuses 62, which are connected in parallel. The total resistance R in each path R1, R2 is calculated by taking into account all the resistances present in the current branch (current-carrying components 60, 62, busbars or circuit board busbars R Cu The total resistance value R FET+FUSE) can be understood as the sum of the current paths R1, R2. Analogously to the described application, any number of components 60, 62 can be connected in parallel. Each current branch is provided with a current measuring device with an associated measuring resistor 64. The respective current measurements I1, I2 and voltage drop U are then fed to a parameter estimator 68, which determines the respective total resistances R1, R2 in the individual current paths. Corresponding voltage measuring points for differential voltage measurement U via measuring amplifiers 66 are provided between the current-carrying elements 60, 62 and the respective measuring resistors 64, as shown. This principle can also be used without restriction for more complex networks, for example by adding additional current paths and additional components, such as switching means 60 and / or fuses 62. In a star point with n branches and thus n string resistances Rn, all string resistances Rn can be monitored by n / 2 differential voltage measuring amplifiers 66.

[0102] As shown in FIG. 9, the entire supply path 59 includes contacts 74 in addition to the current-carrying components 60, 62 and conductor tracks. These act as an interface with the outside world in the control device 78, connecting the supply path 59 inside the control device to an external cable harness. The contacts 74, e.g., plug contacts, are typically connected to a circuit board 76, e.g., by soldering or welding, usually via multiple points or pins. Due to vehicle vibrations and aging, these contacts 74 can deteriorate or even loosen over time. This can significantly impair their ability to carry current. Potential errors exist. For this reason, monitoring the electrical contact characteristics of the contacts 74 is important from a safety perspective.

[0103] The measurement or supply path 59, over which the total resistance R is monitored, can be extended by appropriately placing differential voltage measurement points. If the voltage measurement points are not only placed across current-carrying components such as the switching means 60 and / or fuse 62, as shown in FIG. 9 below, but also on the pins of the contacts 74 of the control device 78, as shown in FIG. 10, the total resistance R of the components 60, 62, the conductor tracks (with associated resistance R Cu) and plug contacts (included resistance R conn ) can be monitored for the total resistance R of the entire current or supply path 59. To do this, one pin of contact 74 is used as a sense line or voltage tap, while the other pin continues to carry current.

[0104] The monitored path can be further extended by routing sense wires or voltage taps outside the control device 78. The monitored current path can include current carrying components such as switching means 60 and / or fuses 62, conductor tracks (R Cu ), and the plug contact system (R conn ) is composed of the whole.

[0105] The power distributor 18 with the associated monitoring circuit 34 is arranged, for example, in a 12V on-board power supply network 13 of a motor vehicle, directly at the interface between a non-safety-related partial on-board power supply network 10 and a safety-related partial on-board power supply network 11, in particular an ASIL-compliant partial on-board power supply network 11. The power distributor 18 includes at least a disconnection / connection module consisting of a main path 30 with associated components 60, 62 and a parallel-connected additional path 50 or supply path 59. However, the application is not limited to this.

Claims

1. 1. A method for monitoring the energy supply of a motor vehicle, comprising: at least one supply path (59) for supplying electrical energy to a safety-relevant load (16, 25); the supply path (59) including at least two current-carrying components (60, 62) connected in parallel and protecting the safety-relevant load (16, 25); the method comprising: determining a value of at least one electrical characteristic quantity (R) representative of the function of the supply path (59); detecting at least one electrical measurement quantity (U, I) applied to at least one of the current-carrying components (60, 62); determining the electrical characteristic quantity (R) as a function of the measurement quantity (U, I); and performing an inspection of at least the electrical characteristic quantity (R); and the current-carrying components (60, 62) and the supply path (59) being at least partially arranged in a control device (78). the electrical measurands (U, I) are a value of a voltage drop (U) across at least one of the current-carrying components (60, 62) and a value of a current (I) flowing through at least one of the current-carrying components (60, 62), For offset correction of the electrical characteristic quantity (R), [Equation 1] Using the formula, the estimated value of the constant overlap (b) [Equation 2] is identified, U represents the voltage drop (U) across at least one of the current-carrying components (60, 62), I represents the value of the current (I) flowing through at least one of the current-carrying components (60, 62), a1 represents a gain coefficient, and R represents an electrical characteristic quantity (R); method.

2. The method according to claim 1, characterized in that the current-carrying components (60, 62) are switching means (60) and / or fuses (62).

3. The method according to claim 2, characterized in that the switching means (60) is a semiconductor switch such as a MOSFET.

4. The method described in claim 1, characterized in that the electrical characteristic quantity (R) is electrical resistance (R).

5. The method according to claim 4, characterized in that the electrical characteristic quantity (R) is the total resistance (R) of the current-carrying components (60, 62) connected in parallel.

6. 2. The method according to claim 1, characterized in that the electrical characteristic quantity (R) is compared with a threshold value and, in case of a significant deviation, an error message (92) is generated.

7. The method of claim 6, wherein the threshold value is a nominal resistance value (Rn).

8. 8. The method of claim 7, wherein said nominal resistance (Rn) is variably selected.

9. 9. The method of claim 8, wherein the nominal resistance (Rn) is variably selected using a resistance model (88).

10. The method of claim 9, wherein the nominal resistance value (Rn) is variably selected using a thermal resistance model.

11. 9. The method of claim 8, wherein the temperature of the current-carrying parts (60, 62) is detected to determine the nominal resistance (Rn).

12. 2. The method of claim 1, wherein the measurements (U, I) are fed to a parameter estimator (68), and the characteristic quantity (R) is constantly updated by the parameter estimator (68) whenever new measurements (U, I) are present.

13. 13. The method of claim 12, wherein the parameter estimator (68) for recursively solving a system of equations U=I*R, where U represents the voltage drop (U) across at least one of the current-carrying components (60, 62), I represents the value of the current (I) flowing through at least one of the current-carrying components (60, 62), and R represents the electrical characteristic quantity (R), is used to determine this electrical characteristic quantity (R).

14. 13. The method according to claim 12, characterized in that the parameter estimator (68) comprises at least one predictor (67) and / or corrector (69) of systematic measurement errors of the measurands (U, I).

15. The method according to claim 1, characterized in that a measuring resistor (64) arranged upstream of the branch to the parallel connection of the supply path (59) is used to detect the value of the current (I) flowing through the current-carrying components (60, 62), and / or a measuring amplifier (66) is used to detect the value of the voltage (U) dropping across the current-carrying components (60, 62).

16. The method of claim 15, wherein the measurement amplifier (66) is a differential amplifier.

17. 2. The method according to claim 1, characterized in that at least one measuring point for detecting the current (I) and / or voltage (U) values ​​of both the current-carrying element (60, 62) and the supply line is arranged at the beginning and / or end of the supply line.

18. The method of claim 17, characterized in that the supply line is a copper wire of a circuit board (76).

19. 2. The method according to claim 1, characterized in that a measuring point for voltage and / or current measurement is arranged at at least one contact (74) of the control device (78).

20. The method according to claim 19, characterized in that the measuring points for the voltage measurement and / or current measurement are arranged at at least two contacts (74) of the control device (78).

21. 2. The method according to claim 1, characterized in that if the measured quantities (U, I) are not up to date, a load pulse is required for an up-to-date determination of the measured quantities (U, I).

22. 2. The method according to claim 1, characterized in that the supply path (59) is arranged between a partial on-board electrical grid (11) for at least one safety-relevant load (16, 25) and a further partial on-board electrical grid (10) for at least one non-safety-relevant load (17).

23. The method described in claim 22, characterized in that the supply path (59) is arranged in a power distributor (18).

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